Although about half the size of Earth, Mars has many things in common with our planet. The Red Planet is known to experience seasons and weather and has polar ice caps and other geological features relating to volcanoes. Mars has two moons, Phobos and Deimos, which were discovered in 1877 by Sir Asaph Hall. Phobos is the closest known satellite orbiting Mars. Mars orbits the sun in 687 days.

Mars can be viewed with ease from Earth and because of this it is not known who first discovered the planet. What we do know is that Mars was named by the Romans and is a reference to their god of war. It was probably given this name because of its red hues and the connotations of blood.

As a rocky planet, the surface of Mars points to a history of volcanic activity and planetary collisions. Its core consists of iron covered by a silicate mantle. Its red colour is attributed to the presence of large quantities of iron on the surface which rust and create iron oxide. The dust from this rust is blown around by the wind and is also present in the atmosphere, which gives off a red glow. Mars’s crust is about 50 km deep.

Mars has many distinctive geological features such as volcanoes and Olympus Mons is the largest volcanically created mountain. It is over 22 km high. The deepest canyon is called Valles Marineris. A smooth area that covers 40 per cent of Mars’s surface is known as the Borealis Basin and is believed to have been created by a huge impact. Water has long been thought to exist on Mars, but because it is such a cold planet most of it is thought to be frozen. Another reason for this is that Mars has a thin atmosphere, which means that water in liquid form would not last long on the surface.

The Mariner 4 spacecraft was the first to fly by Mars in 1965 and sent back data showing it to be a deserted, bleak and heavily cratered planet. In 1976, Viking 1 and 2 landed on the planet and since this time there have been many other landings on the surface of Mars. These missions have collected data relating to its surface and reported on the atmospheric and weather conditions. The Mars Exploration Rovers – Sojourner, Spirit and Opportunity – have all gathered important data which indicates that water was once present on the planet.

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Mars Gallery

A computerised image of sunlight breaking across the surface of Mars

Endeavour crater on Mars, 22km in diameter and 300m in depth

'Homestake' vein on Mars showing powerful evidence for water flow. Discovered on the edge of Endeavour crater

Global view of planet Mars showing weather patterns

Santa Maria crater on Mars, a small impact crater about 80m across

Victoria crater, an impact crater on Mars approx. 750m in diameter and 70m in depth.